1. Field of the Invention:
The present invention relates to wave guides and more particularly to an improved branching filter for branching a wave having one or more frequency bands from a wave having multi-frequency bands through coupling holes disposed on a conical horn.
2. Description of the Prior Art:
Heretofore, when it was desirable to branch a wave having a desirable frequency band from a conical horn propagating a wave having multifrequency bands through coupling holes disposed within the conical horn, to a branching waveguide, the coupling holes have been disposed on the same ridge line of the conical horn depending upon a desirable frequency band for branching.
Accordingly, in the case of desirable frequency bands for branching, having a small frequency differential therebetween the coupling holes have been disadvantageously overlapped.
In order to overcome such disadvantages, a desirable number of circular wave guides and tapered waveguides, corresponding to the number of frequency bands for branching, have been connected in series with coupling holes disposed on a wall of each of the circular waveguides.
However, there have been disadvantages such as the necessity for an axially elongated branching filter and the excitation or generation of higher order mode waves which cause electrical difficulties, and in addition, when the horn is used in conjunction with wide band zones, the circular waveguide connected to the horn becomes excessively large or oversized for high frequency waves.